Concerns associated with the long term fate of wastes and drawbacks associated with current waste disposal methods have led to a variety of different systems designed for the treatment and stabilization of those wastes. Systems which handle a wide variety of waste streams and which produce useful and/or benign products with a minimum amount of secondary waste streams are particularly preferred. Several schemes for achieving these desired ends have been proposed. High temperature systems which destroy waste by converting the inorganic portion of the waste into stable glasses and the organic portion of the waste into a useful synthesis gas are particularly notable. Many of these systems utilize plasmas to generate the high temperatures necessary to form stable, leach resistant glasses and to achieve the gaseous reactions necessary to form useful products such as synthesis gas from organic feed streams.
Plasmas are high temperature, ionized gasses which provide rapid and efficient heat transfer. The ability of plasmas to rapidly transfer heat to incoming organic feedstocks allows the plasma to simultaneously pyrolyze the organic feedstocks and provide the thermal energy to drive the endothermic steam reforming reactions of the pyrolyzed organic feedstocks. This dual benefit has been deployed with great success in systems utilizing plasmas including those described in U.S. Pat. No. 5,666,891, titled “Arc Plasma-Melter Electro Conversion System for Waste Treatment and Resource Recovery” to Titus et al. and which the entire contents are incorporated herein by reference, which shows a variety of particularly useful configurations wherein arc electrodes which produce the plasma are used in systems in various combinations with joule heating electrodes. In these arrangements, organic compounds contained in the waste are destroyed by pyrolysis, caused by the high temperatures of the plasma breaking the chemical bonds of the organic molecules. By introducing steam into the process chamber, these pyrolyzed organic constituents are converted into synthesis gas, a clean burning fuel consisting primarily of CO, CO2 and H2, through the steam reforming reaction. Other constituents of the waste, which are able to withstand the high temperatures without becoming volatilized, are made to form into a molten state which then cools to form a stable glass. By carefully controlling the vitrification process, the resulting vitrified glass may be made to exhibit great stability against chemical and environmental attack, with a high resistance to leaching of the hazardous components bound up within the glass. In this manner, these waste treatment systems may be utilized to convert waste materials into a high quality synthesis gas and a stable, environmentally benign, glass.
While systems utilizing plasma present significant advantages over prior art waste treatment systems, there still exist certain drawbacks related to the incomplete formation of CO, CO2 and H2, through the steam reforming reactions. In particular, plasma and other high temperature systems will occasionally fail to completely convert organic feedstocks into of CO, CO2 and H2, through steam reforming reactions. Typically, incomplete conversion is a result of a failure to either raise the materials to a sufficient temperature to bring about these reactions, or a failure to hold the materials at these high temperatures for a sufficient period of time to allow complete conversion. The incomplete conversion of the gasses and carbon particles adds to the cost of these systems, as equipment must be provided to treat or remove the organic gasses and carbon particles in the off gas of these systems. Thus, there exists a need for a method and apparatus which promotes the conversion of carbon particles, organic gasses and steam into CO, CO2 and H2, through steam reforming reactions.